Integumentary system 36-3

Components

• Skin, hair, nails, and glands

• The body’s covering

• Separates us from the outside world

Skin function

• Protection: barrier against infection and injury

• Temperature regulation

• Removes waste products

• Protects against UV radiation from the sun

Epidermis• Outer layer of skin• Dead cells form the

waterproof, flexible outside layer

• Living cells move upward to replace them

• Melanin: brown pigment that absorbs UV

skin

Dermis

• Has blood cells, nerve fibers• Oil glands keep skin flexible, waterproof• Helps regulate body temp:

• Too cold, hairs stand up, blood vessels narrow.• Too hot: sweating cools, removes wastes • Blood vessels expand to cool blood

Glands of the dermis: sweat glands

• Sweat glands: produce perspiration (water + salts). When the sweat evaporates, it takes heat away from the body.

• Sweat also removes wastes from the blood.

• We produce, on average, 500ml of sweat a day.

• Doing strenuous work or with heat exposure, we can produce10 liters of sweat a day!

Sebaceous glands• Oil glands

produce sebum: an oily secretion, onto the outer layer of skin.

• Sebum keeps the epidermis flexible and waterproof.

• Over-production of sebum leads to acne.

Skin cancer• Abnormal skin

growth, caused by too much UV exposure

• Prevention: sunscreen, hats, clothing.

Basal, squamous, melanoma cancers

Hair • Keratin: makes hair

(also horns, scales, quills and feathers). Is not living tissue.

• Scalp hair: warmth, UV protection

• Nose, eyelash, ear hairs: prevents dirt from entering

• Follicles: living cells at the base push the hair outwards.

Nails

• Cover and protect fingers and toes• Cells of the nail root fill with keratin to

make the tough, platelike nail• Grow 3mm-12mm a month

Review questions

1. What are the main functions of skin?2. What part of the hair is living? What

part of the hair is dead cells?3. Why is it important that skin be

waterproof?4. Why don’t you bleed if you get a

light scratch?5. What can we do to keep our skin

healthy?